The 33st International Electric Propulsion Conference, The George Washington University, USA October 6 – 10, 2013 1 An Experimental Study of Plasma Detachment from a Magnetic Nozzle in the Plume of the VASIMR ® Engine IEPC-2013-123 Presented at the 33rd International Electric Propulsion Conference, The George Washington University • Washington, D.C. • USA October 6 – 10, 2013 Christopher S. Olsen 1 , Maxwell G. Ballenger 2 , Mark D. Carter 3 , Franklin R. Chang Díaz 4 , Matthew Giambusso 5 , Timothy W. Glover 6 , Andrew V. Ilin 7 , and Jared P. Squire 8 Ad Astra Rocket Company, Webster, Texas, 77598, USA Benjamin W. Longmier 9 University of Michigan, Department of Aerospace Engineering, Ann Arbor, Michigan, 48109, USA Edgar A. Bering, III 10 University of Houston, Department of Physics and ECE, Houston, Texas, 77204, USA and Paul A. Cloutier 11 Rice University, Department of Physics and Astronomy, Houston, Texas, 77005, USA Abstract: Understanding the physics involved in plasma detachment from magnetic nozzles is well theorized but lacking in large scale experimental support. We have undertaken an experiment using the 150 m 3 VASIMR ® test facility and VX-200 thruster seeking evidence that detachment occurs and understanding of the physical processes involved. It was found that the plasma jet in this experiment does indeed detach from the applied magnetic nozzle (peak field ~ 2 T) in a two part process. The first part involves the ions beginning to deviate from the nozzle field 0.8 m downstream of the nozzle throat. This separation location is consistent with a loss of adiabaticity where the ratio of the ion Larmor radius to the magnetic field scale length (r Li |∇B|/B) becomes of order unity and conservation of the magnetic moment breaks down. Downstream of this separation region the dynamics of the unmagnetized ions and magnetized electrons, along with the ion momentum, affect the plume trajectory. The second part of the process involves the formation of plasma turbulence in the form of high frequency electric fields. The ion and electron responses to these electric fields depend upon ion momentum, magnetic field line curvature, magnetic field strength, angle between the particle trajectories, and the effective momentum transfer 1 Senior Research Scientist, chris.olsen@adastrarocket.com. 2 Staff Scientist, ballengerm@gmail.com. 3 Director of Technology, mark.carter@adastrarocket.com 4 Chief Executive Officer, info@adastrarocket.com 5 Research Scientist, matthew.giambusso@adastrarocket.com 6 Director of Development, tim.glover@adastrarocket.com 7 Computational Research Lead, andrew.ilin@adastrarocket.com 8 Director of Research, jared.squire@adastrarocket.com 9 Assistant Professor, longmier@umich.edu 10 Professor, eabering@uh.edu 11 Professor Emeritus, pac@rice.edu